usb: dwc3: gadget: Set maxpacket size for ep0 IN

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drivers/usb/dwc3/gadget.c static void dwc3_gadget_conndone_interrupt(struct dwc3 *dwc) · line 2754

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drivers/usb/dwc3/gadget.c +1 -0

index bdf2a2014ebd..6ae924d95cbc 100644
@@ -2751,6 +2751,8 @@ static void dwc3_gadget_conndone_interrupt(struct dwc3 *dwc)
   		break;
   	}
 
+	dwc->eps[1]->endpoint.maxpacket = dwc->gadget.ep0->maxpacket;

thanks :-) I've had that on my list for a while but never got to it since it has no real effects other than reporting properly on tracepoints :-)

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Just to clarify, this is a bug. We found this issue when we test for HS/FS 3-stage control read transfer for ZLP.

interesting... I have never seen such bug before. Got some tracepoints of the problem? Also, if it's a bug, why wasn't it sent as a separate patch with a Cc stable and a Fixes tag?

DWC3 gadget starts with max packet size (mps) 512 as default for ep0. That value should be updated after ConnectDone event when DWC3 checks for the connected speed. In HS/FS, the 3-stage control read transfer sends ZLP based on the mps for IN ep0, but that value is not updated.

Here's a quick test with the 3-stage HS control read.

Setup:
* mass_storage driver
* Modify driver string description to 128 bytes
* Enumerate device in highspeed (mps = 64)

Below is the snippet of trace with GetDescriptor(STRING) request for the driver string description. Device did not prepare and send ZLP packet.

41.787092: dwc3_ctrl_req: Get String Descriptor(Index = 4, Length = 255) 41.787093: dwc3_prepare_trb: ep0in: 0/0 trb 0000000070a29ad1 buf
00000000b8d67800 size 128 ctrl 00000c53 (HLcs:SC:data)
41.787094: dwc3_readl: addr 000000008008901e value 00002400 41.787095: dwc3_writel: addr 00000000831c6d00 value 00000000 41.787095: dwc3_writel: addr 000000003e4167b3 value 37820000 41.787095: dwc3_writel: addr 00000000f504c84e value 00000000 41.787095: dwc3_writel: addr 00000000ca003fac value 00000406 41.787095: dwc3_readl: addr 00000000ca003fac value 00000406 41.787098: dwc3_readl: addr 00000000ca003fac value 00010006 41.787100: dwc3_gadget_ep_cmd: ep0in: cmd 'Start Transfer' [1030]
params 00000000 37820000 00000000 --> status: Successful
41.787101: dwc3_readl: addr 00000000ca003fac value 00010006 41.787103: dwc3_readl: addr 000000007bcb1278 value 80001000 41.787105: dwc3_writel: addr 000000007bcb1278 value 00001000 41.787107: dwc3_readl: addr 000000008eea6144 value 00000000 41.787216: dwc3_readl: addr 000000008eea6144 value 00000008 41.787218: dwc3_readl: addr 000000007bcb1278 value 00001000 41.787219: dwc3_writel: addr 000000007bcb1278 value 80001000 41.787220: dwc3_writel: addr 000000008eea6144 value 00000008 41.787220: dwc3_event: event (0000c042): ep0in: Transfer Complete
[Data Phase]
41.787220: dwc3_complete_trb: ep0out: 0/1 trb 0000000070a29ad1 buf
00000000b8d67800 size 0 ctrl 00000c52 (hLcs:SC:data)
41.787221: dwc3_complete_trb: ep0out: 0/1 trb 00000000cba79c85 buf
0000000000000000 size 0 ctrl 00000000 (hlcs:sc:UNKNOWN)
41.787221: dwc3_gadget_giveback: ep0out: req 00000000fd996780 length
128/128 ZsI ==> 0
41.787221: dwc3_event: event (000010c2): ep0in: Transfer Not Ready
(Not Active) [Data Phase]
41.787221: dwc3_readl: addr 000000007bcb1278 value 80001000 41.787223: dwc3_writel: addr 000000007bcb1278 value 00001000 41.787223: dwc3_readl: addr 000000008eea6144 value 00000000 46.294697: dwc3_readl: addr 000000008eea6144 value 00000004 46.294698: dwc3_readl: addr 000000007bcb1278 value 00001000 46.294699: dwc3_writel: addr 000000007bcb1278 value 80001000 46.294700: dwc3_writel: addr 000000008eea6144 value 00000004

Below is the snippet of the trace with the fix:

34.079018: dwc3_ctrl_req: Get String Descriptor(Index = 4, Length = 255) 34.079020: dwc3_prepare_trb: ep0in: 0/0 trb 000000006ece9b4d buf
00000000b8d67800 size 128 ctrl 00000455 (HlCs:Sc:data)
34.079020: dwc3_prepare_trb: ep0in: 0/0 trb 000000001b323efa buf
0000000037821000 size 0 ctrl 00000c53 (HLcs:SC:data)
34.079020: dwc3_readl: addr 00000000a90978f8 value 00002400 34.079021: dwc3_writel: addr 00000000c8f7ea9f value 00000000 34.079021: dwc3_writel: addr 000000000217f085 value 37820000 34.079021: dwc3_writel: addr 00000000b5593ec9 value 00000000 34.079021: dwc3_writel: addr 000000008b9e5492 value 00000406 34.079022: dwc3_readl: addr 000000008b9e5492 value 00000406 34.079024: dwc3_readl: addr 000000008b9e5492 value 00010006 34.079027: dwc3_gadget_ep_cmd: ep0in: cmd 'Start Transfer' [1030]
params 00000000 37820000 00000000 --> status: Successful
34.079027: dwc3_readl: addr 000000008b9e5492 value 00010006 34.079029: dwc3_readl: addr 00000000e9897a1c value 80001000 34.079031: dwc3_writel: addr 00000000e9897a1c value 00001000 34.079031: dwc3_readl: addr 0000000034bddbfc value 00000000 34.079144: dwc3_readl: addr 0000000034bddbfc value 00000004 34.079146: dwc3_readl: addr 00000000e9897a1c value 00001000 34.079147: dwc3_writel: addr 00000000e9897a1c value 80001000 34.079148: dwc3_writel: addr 0000000034bddbfc value 00000004 34.079148: dwc3_event: event (0000c042): ep0in: Transfer Complete
[Data Phase]

34.079148: dwc3_complete_trb: ep0out: 0/1 trb 000000006ece9b4d buf
00000000b8d67800 size 0 ctrl 00000454 (hlCs:Sc:data)
34.079149: dwc3_complete_trb: ep0out: 0/1 trb 000000001b323efa buf
0000000037821000 size 0 ctrl 00000c52 (hLcs:SC:data)
34.079149: dwc3_gadget_giveback: ep0out: req 00000000bbc62204 length
128/128 ZsI ==> 0
34.079149: dwc3_readl: addr 00000000e9897a1c value 80001000 34.079150: dwc3_writel: addr 00000000e9897a1c value 00001000